1. Field of the Invention
The present invention relates to an inkjet printing apparatus that uses inks to form an image.
2. Description of the Related Art
In inkjet printing apparatus using ink with lower solubility than conventional ink (hereinafter referred to as easily settling or sedimenting ink), when ink is repetitively ejected onto an ink receiver during a marginless printing and a cleaning ejection—an operation which ejects ink not for printing but for cleaning nozzles of a print head—the ejected ink may settle in the ink receiver or flow path, clogging the flow paths or forming ink sediments on the ink receiver. The ink sediments may flow out of the ink receiver, contaminating its surroundings, smearing a print medium or coming into contact with a print head face formed with nozzle openings. So, in the printing apparatus using easily sedimenting inks, a control to prevent sedimentation of ink constitutes an important technical issue.
To deal with this problem of the conventional inkjet printing apparatus, Japanese Patent Laid-Open No. 2008-62609 offers a technique that determines the amount of sedimentation restraining inks, that needs to be ejected onto a platen ink absorber to prevent ink sedimentation on it, in relation to the amount of easily sedimenting inks and which measures the volume of, or performs dot counting of, each ink color applied to each of divided regions of the platen ink absorber and determines with high precision an amount of sedimentation restraining inks to be applied to each region.
The conventional technique determines the amount of sedimentation restraining inks based on the dot count of easily sedimenting inks. It claims to be able to determine the amount of sedimentation restraining inks with high accuracy by dividing the platen ink absorber into a plurality of regions and performing dot counting in each of the regions. That is, it determines the amount of sedimentation restraining inks to be applied by considering only the amount of easily sedimenting inks already ejected.
The amount of sedimentation restraining inks for preventing ink sedimentation should be determined by considering not only the amount of easily sedimenting inks but also a component ratio of the easily sedimenting inks, a state of the platen ink absorber and a remaining ink volume. Japanese Patent Laid-Open No. 2008-62609 therefore has a problem that, in some cases, it may not be able to determine or eject an appropriate amount of sedimentation restraining inks for preventing ink sedimentation.